Goalposts

I am thoroughly unimpressed by GPT-5. It still can't compose iambic trimeters in ancient Greek with a proper penthemimeral cæsura, and it insists on providing totally incorrect scansion of the flawed lines it does compose. I corrected its metrical sins twice, which sent it into "thinking" mode until it finally returned a "Reasoning failed" error.

There is no intelligence here: it's still just giving plausible output. That's why it can't metrically scan its own lines or put a cæsura in the right place.